Four big Wisconsin counties played crucial roles in Democrat Tammy Baldwin's victory over Republican Tommy Thompson in the race for U.S. Senate.

Baldwin performed significantly better on Tuesday in Kenosha, Racine, Brown and Milwaukee counties than did fellow Democrat Russ Feingold when he lost two years ago to Republican Ron Johnson.

There are numerous reasons for Baldwin's win against the former governor, who was the front-runner going into the race.

A day after the election, experts attributed Baldwin's victory to the coattail effect of the presidential race, her funding edge in the early going and her ability to exploit issues such as Thompson's lucrative career in business built on government connections.

These and other factors helped Baldwin pick up votes in key counties that were instrumental to her victory.

"I think she ran a more rigorous race than Tommy," said Joe Heim, a University of Wisconsin-La Crosse political scientist. "She seemed to get around the state more than he did."

In Kenosha County, Baldwin took 54.2% of the vote. Feingold had 46.8% in 2010.

In Racine County, Baldwin took 51%. Feingold had 43.4%.

Baldwin and Feingold both lost to their Republican challengers in Brown County. But Baldwin's share of the vote was 48% - up from Feingold's 42% share.

In Milwaukee County, she increased her share of the vote to 65.7% from Feingold's 61.3%, driven by strong voter turnout in Milwaukee for President Barack Obama.

The four counties accounted for a net swing over Feingold's performance in 2010 of 167,462 votes.

Baldwin beat Thompson by 163,204 votes in the most expensive Senate election in Wisconsin history.

Baldwin and Feingold won the same percentage of the vote in Dane County. Seven in 10 voters in each election went with the Democratic candidate.

Baldwin also had a strong showing in western and southeastern Wisconsin, while Thompson, as expected, was strong in suburban Milwaukee and eastern counties.

Heim thought Thompson might have picked up more voters who split their ticket with a vote for Thompson and vote for Obama. In exit polls, just 3% of the electorate voted that way.

"Neither of them were close to the middle, in my opinion," Heim said of Baldwin and Thompson. "I thought Thompson could move to the middle, but he seemed reluctant to do that."

Pollster Charles Franklin of the Marquette University Law School sees a "hint of a national force" working in the election, with Democrats in Missouri, Indiana, Virginia and North Dakota - among other states - also winning tough races.

Franklin is a political scientist who will be returning to the University of Wisconsin-Madison next year after a year of polling at Marquette.

He said his polls revealed unfavorable attitudes toward both Thompson and Baldwin. But on the question of who cared more for people like those who were polled, Baldwin always came out on top, he said.

Baldwin also benefited on the issue of Medicare. She supports the current framework, and Thompson endorsed wholesale changes sought by U.S. Rep. Paul Ryan, the vice presidential candidate. He later modified his stance. Polling showed voters strongly prefer the current system, even though it faces financial jeopardy.

Ben Poston of the Journal Sentinel staff contributed to this report.

About Lee Bergquist

Lee Bergquist covers environmental issues and is author of "Second Wind: The Rise of the Ageless Athlete."